15:00:13 RRSAgent has joined #tt 15:00:13 logging to https://www.w3.org/2021/07/08-tt-irc 15:00:15 RRSAgent, make logs Public 15:00:17 Meeting: Timed Text Working Group Teleconference 15:00:57 Agenda: https://github.com/w3c/ttwg/issues/192 15:01:42 Present+ Nigel, Cyril, Gary 15:01:46 scribe: nigel 15:02:01 Previous meeting: https://www.w3.org/2021/06/24-tt-minutes.html 15:02:29 Present+ Andreas 15:03:38 Present+ Pierre 15:04:34 Chair: Gary, Nigel 15:04:44 Topic: This meeting 15:05:06 Nigel: Today we have: 15:05:11 * IMSC HRM Strategy 15:05:19 s/*/..* 15:05:38 .. * one open TTML2 issue, and 15:05:42 .. * Tests 15:05:50 .. * Plus AOB: TPAC. 15:06:04 .. Is there any other business, or anything to make sure we cover? 15:06:15 group: [silence] 15:06:25 Topic: IMSC HRM Strategy 15:07:00 Pierre: The problem is straightforward. 15:07:20 mike has joined #tt 15:07:23 .. There are 3 versions of IMSC that are current: 1.0.1, 1.1 and 1.2. 15:07:29 .. 1.0.1 and 1.1 are maybe most used. 15:07:37 .. They all define the Hypothetical Render Model that 15:07:44 .. allows the complexity of documents to be bounded. 15:07:53 .. In the process of writing an HRM validator I have found some issues. 15:08:12 .. In all cases, the question is: if we modify the HRM, how do we propagate it throughout all the versions, or not. 15:08:20 s/t./t? 15:08:25 .. What's the right way? 15:08:29 .. Errata against each? 15:08:32 .. Revise each? 15:08:37 .. Factor out the HRM? 15:08:43 .. I'd appreciate people's input and thoughts. 15:09:09 Cyril: Factoring it out seems like the best option to me, avoiding discrepancies. 15:09:23 .. Is it totally possible? Are there features that need specific provisions in the HRM? 15:09:35 Pierre: Yes, I think the answer is yes actually, there are differences, which also could be factored out. 15:10:10 .. 1.1 added text shadow. So there's at least one difference. 15:10:21 .. That had to be included in the HRM. 15:10:34 .. In terms of process, how difficult is it to revise an edition? 15:12:02 Nigel: It's doable. The choice is to revise three Recs or publish a 4th Rec and revise 3 Recs. But I think it might be worth it. It's certainly tempting. 15:12:08 Pierre: What's the process for revising an edition? 15:12:13 Present+ Atsushi 15:12:23 present+ 15:12:33 atai has joined #tt 15:13:52 Nigel: I think all those Recs were published before we could adopt the new mechanism for making candidate changes in Recs. 15:13:59 .. Does that mean we cannot now start doing that? 15:14:21 .. Or can we say "hey, we're going to work like this now" on these existing Recs? 15:14:44 Atsushi: I need to check. In any case we need to go through CR -> Rec for substantive changes. 15:14:53 .. When we go to CRS we can adopt the new mechanism. 15:15:02 .. I suppose the answer is Yes, or it will be automatically applied. 15:15:19 cyril has joined #tt 15:16:08 .. As an example, CSS [something] published in 2020 went through that change. I can't recall exactly which. 15:16:38 -> https://www.w3.org/2020/Process-20200915/#update-reqs 6.2.4. Updating Mature Publications on the Recommendation Track 15:18:37 CSS containment module level 1 -> https://www.w3.org/TR/2020/REC-css-contain-1-20201222/ 15:19:27 Atsushi: This is the first one that was updated under Process 2020. You can see in the history... 15:19:36 Nigel: Oh yes, it went from Rec to Rec. 15:20:24 .. I see, Candidate Corrections were inserted. 15:20:36 Atsushi: It may be possible to follow this since it is the same situation. 15:21:45 Present+ Mike 15:23:09 Mike: The challenge is if the HRM is different across versions, then it gets trickier and harder to reference. 15:24:05 Nigel: Is the text shadow change one where there's something countable where the count comes to zero when the feature is prohibited? 15:24:21 Pierre: Yes, that's a really easy one. I think it's the only one, so it makes the refactoring option not impossible. 15:27:05 q+ 15:27:34 Nigel: Is now a good time to push a message out to the world to say we're thinking about an HRM Rec and asking for interested implementers 15:27:36 .. to come forward? 15:27:54 Pierre: Are two implementations needed? 15:28:18 Nigel: The rules in 6.2.4.1 are stricter than 6.2.2 deliberately. It may actually be easier to justify a separate Rec track document. 15:28:32 Andreas: Are existing implementations meeting the spec? 15:28:42 Pierre: This is a good moment to check. 15:29:06 Andreas: At the moment the most used implementations are imscJS or TTPE so this would be two implementations 15:29:22 Pierre: But the HRM tests complexity of documents so if we want to make sure the reference implementation is correct we would 15:29:29 .. have to test against creation tools. 15:29:41 Mike: It's a constraint on the encoder rather than the player. 15:29:58 Pierre: This is the time to do this, whatever we do if we are going to modify the specs, part of the implementation 15:30:08 .. experience is to get confidence that it works against implementations in the wild. 15:30:18 ack at 15:31:10 Nigel: Thinking out loud, I wonder if there's a way of framing this that we have both a validating implementation 15:31:27 .. and a player implementation where the player can play documents of the maximum complexity. 15:32:15 Nigel: Just to remind ourselves of the changes... 15:32:24 -> https://github.com/w3c/imsc/issues?q=is%3Aissue+is%3Aopen+label%3Ahrm Issues labelled HRM 15:32:28 Pierre: There are 3 issues. 15:33:38 Nigel: One was uncontroversial, one has an action to prepare the pull request and the third needs further discussion. 15:34:06 Pierre: From an Editor's perspective, thinking out loud, refactoring might be less work, because keeping 15:34:17 .. track of changes across 3 documents might be harder than keeping it all in one document. 15:34:29 .. 4 documents need to be modified, but for 3 it is just deleting a section. 15:34:50 .. We're talking about conformance though. Today, conformance of the Processor 15:34:58 .. is that it should be able to decode all documents that pass the HRM. 15:35:08 .. If we move the HRM to a separate document I don't know how that works. 15:35:17 Mike: You'd have to reference it normatively. 15:35:31 Pierre: [wonders if the HRM references IMSC] 15:35:42 Mike: The end result has to be the same outcome modulo any changes we want to make. 15:35:54 .. We don't want to make a version of IMSC 1 that no longer requires the HRM. 15:36:05 Pierre: Exactly. I just want to avoid circular references. 15:36:19 .. It's possible that the HRM only refers to TTML, in which case that would work. 15:37:37 Nigel: Wonder if we should factor the threshold values out of the HRM and pass them in as parameters from the referring spec. 15:37:55 .. That could make it easier to publish future versions of IMSC with greater threshold values. 15:37:58 Pierre: We could do that. 15:38:44 Mike: We need to increment the versions somehow so that referring specifications are clear. 15:38:55 Pierre: One option is to update 1.1 and 1.2 but not 1.0.1 15:39:06 Mike: That would work for the things I'm concerned about. 15:39:25 Pierre: There are HRM bugs that affect 1.0.1, but I'm not sure there's much risk in having a 2nd edition of 1.0.1 15:39:40 Mike: Maybe that'd be okay, but it's still different. I'm not sure how they would finesse that. 15:40:26 Nigel: It could be 1.0.2, right? It would fix the referencing issue. 15:40:38 .. What would be annoying would be to go from 3 active Recs to 6 though! 15:40:48 Pierre: I don't sense a particular preference from the group. 15:41:05 Mike: Remember the players are in devices that have a lifetime of several years. 15:41:14 .. Proliferation of IMSC specs is not ideal. 15:41:39 Pierre: My suggestion is to start with pull requests on 1.1 and see how it goes. 15:42:35 Nigel: I think signals, even private ones, about intent to implement the HRM would be really helpful here. 15:42:41 Pierre: Why not announce that? 15:43:12 .. My proposal is to make a plan to edit 1.1, to create a new edition, that addresses those issues identified in the HRM, 15:43:33 .. and solicit both other HRM implementations, but even more importantly, sample documents, and help from the industry 15:43:41 .. to test at least the existing HRM implementation. 15:44:26 Nigel: One question I have is what the actual benefit is to fixing the bugs - even though the HRM might be imperfect, 15:44:36 .. it could that it is nevertheless good enough to achieve its goal. 15:44:44 Pierre: Yes, it could be there is a problem or no problem. 15:45:17 Mike: I think there is generally low knowledge of the HRM, but it is being socialised more at the moment. 15:47:28 Pierre: So start with 1.1, and announce the work, and start doing it. 15:47:40 Nigel: That sounds like an action for me to start work on an announcement. 15:47:55 .. We can defer the decision about exactly how we do it. 15:48:04 Pierre: Exactly 15:48:50 Mike: Several specs are locked to 1.0.1 and 1.1 so there would be some logistics to keep this straight and not mess up MPEG, ATSC and DVB. 15:49:12 Nigel: Thanks, let's wrap this topic up. 15:49:52 Topic: Fix #1232 by clarifying the [resolve timing] procedure w3c/ttml2#1233 15:49:57 github: https://github.com/w3c/ttml2/pull/1233 15:50:42 Nigel: After we discussed this last, Pierre, Glenn and I talked about it directly and worked on a change, which I pushed. 15:50:56 .. Glenn approved it, 13 days ago, and nobody else has done. 15:51:33 .. I want to know if we can merge this. It's beyond our normal process time for reviewing, and has one approval. 15:51:37 .. Does anyone want more time to review? 15:53:18 Pierre: It's a great improvement by the way. The only thing that's not clear to me is the wording about the 15:53:28 .. Root Temporal Extent, which has a begin and an end. 15:54:00 Nigel: In our discussions, Glenn and I understood that the Temporal Extent is a duration. 15:54:16 Pierre: But it's in the definition, the Root Temporal Extent has a begin and an end. 15:54:26 Cyril: +1 it has a begin and end 15:54:53 Pierre: If Root Temporal Extent did not have a begin and end, then the application could not modify the begin, and that would be unhelpful. 15:55:05 Nigel: Please could you add the comment to the PR? 15:55:10 Pierre: Yes, sorry for not doing it earlier. 15:55:23 SUMMARY: More review time requested. 15:55:36 Topic: Tests 15:55:44 Nigel: This is a plea from me as Chair! 15:56:00 .. In many ways the tests we have are almost more important than the spec text! 15:56:09 .. Many implementers look at tests first. 15:56:39 .. A number of tests have been added to TTML2 Tests and merged without review, by Glenn. 15:56:53 .. Also there are open pull requests to add tests to IMSC Tests that have not had review. 15:57:40 .. So my request is please everyone do take a look at the tests that are added either directly or by opening pull requests, 15:57:44 .. and watch those repos. 15:58:39 -> https://github.com/w3c/ttml2-tests/ TTML2 Tests 15:59:00 -> https://github.com/w3c/ttml2-tests/pulls?q=is%3Apr+is%3Aclosed+label%3A%22merged+without+review%22 TTML2 Tests merged without review 15:59:15 .. There are 4 recently that I noticed. 16:00:03 Pierre: Looking at #270 and #271 I don't even understand what the issue is. 16:03:09 .. I think it's unfair to ask everyone to review things that can't really be reviewed. 16:03:39 Nigel: I understand. The situation is different on imsc-tests by the way! 16:03:47 -> https://github.com/w3c/imsc-tests/ IMSC Tests repo 16:04:27 Pierre: Yes, I apologise for not reviewing them 16:04:50 Nigel: I see that there are 5 open PRs that no doubt are all good, going back to October 2019, by 3 different contributors. 16:05:00 .. Let's try to carve out time to get those done. 16:05:06 Pierre: I agree 16:05:42 Topic: Meeting Close 16:05:51 Nigel: Thanks everyone, apologies for going 5 minutes over. 16:06:00 .. [adjourns meeting] 16:06:06 rrsagent, make minutes 16:06:06 I have made the request to generate https://www.w3.org/2021/07/08-tt-minutes.html nigel 16:30:03 s/by the way!/by the way. 16:30:17 Present- atsushi 16:30:21 rrsagent, make minutes 16:30:21 I have made the request to generate https://www.w3.org/2021/07/08-tt-minutes.html nigel 16:32:46 rrsagent, make minutes 16:32:46 I have made the request to generate https://www.w3.org/2021/07/08-tt-minutes.html nigel 16:35:40 Present+ Atsushi 16:35:59 rrsagent, make minutes 16:35:59 I have made the request to generate https://www.w3.org/2021/07/08-tt-minutes.html nigel 16:36:30 Present: Andreas, Atsushi, Cyril, Gary, Mike, Nigel, Pierre 16:36:31 rrsagent, make minutes 16:36:31 I have made the request to generate https://www.w3.org/2021/07/08-tt-minutes.html nigel 16:36:54 Present: Andreas, Atsushi, Cyril, Gary, Mike, Nigel, Pierre 16:36:55 rrsagent, make minutes 16:36:55 I have made the request to generate https://www.w3.org/2021/07/08-tt-minutes.html nigel 16:42:18 rrsagent, make minutes 16:42:18 I have made the request to generate https://www.w3.org/2021/07/08-tt-minutes.html nigel 16:42:42 scribeOptions: -final -noEmbedDiagnostics 16:42:45 zakim, end meeting 16:42:45 As of this point the attendees have been Andreas, Atsushi, Cyril, Gary, Mike, Nigel, Pierre 16:42:47 RRSAgent, please draft minutes v2 16:42:47 I have made the request to generate https://www.w3.org/2021/07/08-tt-minutes.html Zakim 16:42:50 I am happy to have been of service, nigel; please remember to excuse RRSAgent. Goodbye 16:42:54 Zakim has left #tt 16:43:20 rrsagent, make minutes 16:43:20 I have made the request to generate https://www.w3.org/2021/07/08-tt-minutes.html nigel 18:54:47 rrsagent, excuse us 18:54:47 I see no action items